Development of improved hybrid rice seed production technologies

Success in hybrid rice seed production (HRSP) is influenced by factors such as local climatic conditions, characteristics of the parental lines, and cultural management practices, among other things. Improving the HRSP efficiency by augmenting seed yield and optimizing production cost/ha can be partly achieved through constant technological refinement catering to location-specific needs. Experiments conducted at the Philippine Rice Research Institute (PhilRice) showed that parental lines of PSB Rc72H (Mestizo) seeded at different months exhibited differences in flowering time. Thus, there is a need to adjust the seeding interval between male and female parents based on their difference in number of days to flowering. Furthermore, it was observed that delayed transplanting, resulting in older seedlings, consequently delayed the flowering of those parents. Since this effect was less pronounced in Cytoplasmic Male Sterile (CMS) line, the chances of nonsynchronization of flowering was increased. Studies on gibberelic acid (GA3) use indicate that increasing the dosage from 80g/ha to 150-200g/ha further enhanced the panicle exsertion and seed setting rates by about 11% and 5%, respectively. Applying this rate in three splits (1st = 25%, 2nd = 50%, 3rd = 25%) beginning at 5% heading showed more effectiveness than two-split application. With these improvements, hybrid seed yield consequently increased. Plant population can be optimized by adjusting the row ratio (R:A) from 2:8 to 2:12 during dry season (DS). This was made possible by the fact that DS normally offers favorable condition for pollination. Better results could be attained when a plant spacing of 20 X 15cm (row x hill) is used. Moreover, planting 3 R line and 2 A line seedlings per hill gave significantly higher seed yield due to increased tiller and panicle number per unit area. Experiences over the past years have shown that HRSP in the Philippines is more viable during the DS, wherein yields increase about two to three folds higher compared with wet season (WS). This is mainly attributed to more favorable weather condition and lesser occurence of pests and diseases